Adding an additional 2 channel audio track to every MKV file, possible?

I need to add a 2 channel stereo audio file to every one of my movies that have multi-channel audio and make it the default audio stream. I want to keep the original audio streams and add a 2 channel AAC file as default to all movies that have 5.1 audio so they play easier on all platforms in EMBY.

Is there a way for me to do this durinf the original conversion from recorded TV to MKV or is this something I have to do manually to every file using some combination of other software? If MCEBuddy can do this for the original conversion is there any way to reprocess all the movies I have to simply add the audio file?

If I have do do this manually can you please make some suggestions on what software to use?

I have 3100 movies on this server and really don’t want to do this manually if I don’t have to.

Thanks.

See this topic:

Thank you, if I am successful translating that is there a way to reprocess my already converted files that are now MKV so as to just add the new audio track without any video processing so I don’t have to do it manually for over 3000 files?

Is there anyone who can translate that for me. It’s Greek to me and I want to keep whatever audio streams are currently in my recordings, which are mostly 2 6 channel audio streams, and add the AAC stereo as default so I don’t quite understand from that information what I would have to do in order to do what I want.

If you just want to add an additional 2 channel AAC track to your existing files (and preserve the original video and audio without re-coding it), then select one of the Unprocessed profiles and replace the appropriate lines with:

ffmpeg-audio=-map 0:1 -map 0:1 -c:a:0 aac -ab 192k -ac 2 -c:a:1 copy
ffmpeg-audioac3=-map 0:1 -map 0:1 -c:a:0 aac -ab 192k -ac 2 -c:a:1 copy
ffmpeg-AudioOptimized=true